JPS6252087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for replacing mixed mud water in an underground wall construction method.

Conventionally, as one of the methods of excavating vertical holes when constructing earth retaining walls, water-stopping walls, foundations of structures, or underground walls as part of underground structures, the inside of the vertical holes to be excavated is stabilized with bentonite or other materials. The so-called stable liquid excavation method is widely used, in which the ground is filled with mixed mud to which liquid has been added to form an impermeable film of stabilizing liquid called Matsudo film on the excavated wall surface, and the ground is excavated while preventing the ground from collapsing.

For example, as shown in Figure 1 in the vertical hole excavated by the above method, there is a need to secure joints at both ends of the vertical hole a and to protect the ends of the concrete to be poured from damage caused by the excavation of subsequent elements. The interlocking pipes b and b are placed inside to secure a wrap space for the horizontal reinforcing bars when the concrete wraps around the back of the partition steel plate, and to prevent earth and sand from flowing into the joint part when excavating the subsequent element. Locking boxes c and c for prevention are arranged on the locking pipe b in such a manner as to take a reaction force.
Then, a partition iron plate d to prevent poured concrete from flowing out and a reinforcing bar cage f with joint reinforcements e attached to both ends for connection with subsequent elements are built in the center of the vertical hole a, and between the partition iron plates d and d. Concrete g is poured. If the poured concrete g is left in this state for several days until it solidifies, a large amount of bentonite will adhere to the joint strips e in the muddy water, reducing the strength when concrete is poured to connect with subsequent elements. Bentonite mud water h in the area surrounded by locking box c was replaced with fresh water to avoid water leakage.

However, according to the above-mentioned conventional method, the work efficiency is poor because the replacement work is carried out in extremely restricted conditions, and the difference in specific gravity between the fresh water in the locking box and the surrounding muddy water causes the replacement work to be carried out from the gap between the locking boxes. There were disadvantages such as muddy water flowing in or when the locking box was removed, the bentonite muddy water was diluted and the water-stopping performance was reduced.

Therefore, in order to solve the above-mentioned drawbacks of the conventional technology, the present invention aims to add CMC (sodium carboxylic acid) mixed mud containing a stabilizing liquid such as bentonite to supplement the properties of the stabilizing liquid without reacting with the cement content immediately after the completion of excavation of a vertical hole. The purpose of this project is to provide a new construction method in which the base material is replaced with a mixed solution containing methyl cellulose, etc. as the main ingredient.

Embodiments of the present invention will be described in detail below with reference to the drawings of FIGS. 2 to 4. First, as shown in FIG. A suction pipe 4 connected to a suction pump 3 is suspended from the bottom of the vertical hole 2 immediately after excavation is completed, and a displacement damper 5 is provided at the top.

This displacement damper 5 has a secondary discharge port 5a in the upper part that communicates between the inside and outside, as shown in the partially cutaway front view in FIG. 3 and the cross-sectional view taken along the line in FIG.
The outer cylinder 5b is arranged side by side, and the inner cylinder 5d has primary discharge ports 5c in three directions at the bottom thereof. It is formed in such a manner that it is opened to form an injection port 5e.

Then, from the injection port 5e, CMC is used as the main agent,
The specific gravity of the mixture with appropriate dispersant, etc. as required is approximately
1.01 to 1.03, specific gravity of bentonite mixed mud 1 is 1.03
A solution at least lighter than ~1.10 is injected as the replacement liquid 6, and the suction pump 3 is operated to discharge the mixed mud water 1 at the bottom from the suction pipe 4.

As a result, the replacement liquid 6 is discharged from the primary discharge port 5c of the inner cylinder 5d into the outer cylinder 5b.
While rising along the inner circumference, the upper secondary discharge port 5a
The bentonite mixture flows out gently onto the bentonite mixed mud water 1. All of the bentonite mixed mud 1 in the vertical hole 2 is sequentially replaced with the replacement liquid 6 without mixing due to the difference in specific gravity.

The subsequent process is the same as the conventional construction method, in which the interlocking pipe and locking box are vertically installed and the reinforcing cage is erected, and then the replacement liquid 6 in the partition iron plate is replaced with concrete and concrete is poured.

In addition, in order to discharge the mixed mud 1, a sand pump or other known arbitrary means can be used in addition to the above, and the substitute liquid 6 and the substitute liquid 6 can be made to have approximately the same specific gravity value without reacting with the cement component. Any material may be used as long as it satisfies the conditions for reinforcing bentonite.

As described above, according to the proposed construction method, immediately after excavating the vertical hole 2, bentonite-mixed mud water 1 is formed in the entire area of the vertical hole 2.
CMC that does not react with the cement content of concrete
Since the substitution liquid 6 is used as the main ingredient, bentonite will not adhere even if it is left immersed in the substitution liquid 6 for a long period of time after concrete is placed inside the partition iron plate. During this process, good concrete placement is achieved without gelation of the concrete, and sufficient strength is ensured. Furthermore, since the replacement work is carried out without obstacles such as reinforcing bar cages, the work can be carried out easily and efficiently.

Furthermore, even with the conventional construction method, an impermeable mud film 7 made of bentonite remains on the wall surface of the vertical hole 2 even after fresh water has been replaced, but the replacement liquid 6 such as CMC of the present application may increase the viscosity of the mud film 7. It has various practical effects such as reinforcement such as improving moldability and further improving water-stopping properties.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional method, Fig. 2 is an explanatory diagram of the inventive method, Figs. 3 and 4 show the replacement damper, Fig. 3 is a partially cutaway front view, and Fig. 4 is an explanatory diagram of the conventional method. The figure is a sectional view taken along the line - in FIG. 3. [Explanation of symbols], 1... bentonite mixed mud water, 2...
Vertical hole, 3... Suction pump, 4... Suction pipe,
5... Displacement damper, 5a... Secondary discharge port, 5b...
Outer cylinder, 5c...primary discharge port, 5d...inner cylinder, 5e...inlet, a...vertical hole, b...locking pipe, c...locking box, d...partition iron plate, e...joint bar, f...rebar cage , g... Concrete, h... Bentonite mud water.

Claims (1)

[Scope of Claims] 1. In a method of constructing an underground wall in a vertical hole excavated by the stabilized liquid drilling method, the vertical hole to be excavated is filled with mixed mud to which bentonite is added as a stabilizing liquid, and the excavation is completed. An underground wall characterized by replacing the mixed muddy water in the entire area inside the vertical hole immediately after with a replacement liquid that is a solution that reinforces bentonite and does not react with cement, and whose specific gravity is lighter than that of the bentonite mixed muddy water. Method for replacing mixed mud water in construction methods. 2 The replacement liquid has a specific gravity of approximately 1.01 to 1.01 and is based on CMC (sodium carboxymethylcellulose).
1. The method for replacing mixed mud water in an underground wall construction method according to claim 1, wherein the mixed solution is 1.03.